Another version/meaning of gedcom is genealogical format for a family tree that most genealogical software will accept. You can upload your "gedcom" (family tree information) to other sites or types of software if you have it in a format that most genealogical sites/software will accept. Many types of software and genealogical sites will let you "export" your family tree in a gedcom format. It is usually a file name that ends ".ged". Then it can be transferred ("imported") to another site or a different software.
You may be thinking about the difference between the site (GEDmatch.com)'s ability to upload raw DNA and also the ability to upload a GEDcom (or family tree). Some people confuse the two things because they sound almost the same.
The "raw DNA" upload is some sort of digital version of your DNA that the site can compare to other people's DNA. The GEDcom is based on paper research and knowledge that links your ancestors together in a tree, hopefully with documentation to back up the paper trail. If you know your great grandfather is "John Jones", and someone else has uploaded a GEDcom (family tree) that also has "John Jones" born around the same place and time, you'll have an idea why you might match this other person.
I hope that makes sense.
Reba
